This is the worst service ever (expensive, hard to understand)! You must pay for any transaction (like make offer to sell or cancel offer to sell), OMNI is impossible to sell (there are only two other exchange services, which have bad reviews and Omniwallet itself with terrible system which almost nobody use now). I had stuck transaction, I have to send money to unstuck it, after I unstack it, support told me, that I will not get any money back, because there are none. So how I could have stuck offer and pay for unstuck of nothing?! Big cheating system is it, nothing more!